The overall goal of this study is to assess the value of potassium-magnesium citrate in preventing hypokalemia and magnesium depletion in patients taking diuretics. The hypothesis to be tested is that K-Mag Citrate is capable of meeting these objectives because of its high bioavailability. If the above goal is met, an ancillary goal will be to examine the effect of K-Mag Citrate in magnesium depletion of non-diuretic use.